Eyeball your average Chinese crowd and they certainly appear lithe, while shopping for clothes in the local market quickly confirms that the majority of Chinese women are pretty small. I have been dismayed to be handed an XL on more than one occasion, and even more upset to find it fits. Nevertheless, it is now estimated that a fifth of the world's billion or so overweight or obese people live in China - yes, there are an awful lot of people in China but that is still a worrying statistic.

Obesity is a defined as having "abnormal or excessive fat accumulation that may impair health" and is currently classified by the World Health Organization (WHO) according to body mass index (BMI). This is a calculated by dividing weight (kg) by height (square meters) with a BMI of 25+ being overweight and 30+ being obese. Such cut off points have been set as a result of studies in white populations showing that health risks for many different diseases are markedly increased at these points. This portfolio of diseases includes cardiovascular disease (high cholesterol, high blood pressure, heart attack), type 2 diabetes, osteoarthritis and cancer.

It is argued that BMI is an inaccurate measurement for some groups - and certainly many athletes in the peak of health fall into the "obese" category based on BMI when this is clearly not the case. Waist circumference (WC) measurements are increasingly used by health professionals as fat carried around the abdomen presents a greater health risk. For white populations men with a WC of greater than 102cm, and women greater than 88cm are considered obese.

Interestingly people of Asian origin (including the Chinese) tend to have a higher percentage of body fat at any given BMI and as a result are at higher risk for associated the diseases at a lower BMI. The WHO has suggested lower cuts offs for these populations and indeed the Chinese government uses a lower classification of 24+ as overweight and 28+ as obese within China. This means that current obesity statistics reported by the WHO for China may underestimate the problem.

The speed at which the "obesity crisis" has developed in China is most concerning, especially with children's overweight and obesity rates increased 28 times between 1985 and 2000. The total number of obese people in China is thought to have doubled to 120 million between 1991 and 2007. Explanations of course lie with rapid economic development and urbanization. Car ownership has increased from 6 million to more the 20 million in the last 20 years, and with the move to the cities people are leading more sedentary lifestyles. Affluence has led to huge changes in the traditional diet with a higher percentage of energy coming from animal products - this rose from 8 percent in 1982 to 25 percent in 2002. The average fat intake in China is now 35 percent of total energy - above the healthy recommendation of 30 percent; vegetable oil consumption per person has increased from 1L to 17L per year in the last 20 years.

That said, China is still a model for many part of the world. In 2005 estimates for the prevalence of overweight and obesity in people 15 years and over was 74.1 percent in the USA, 63.8 percent in the UK and only 28.9 percent in China.

(China Daily 08/23/2007 page14)